Fuse



Mmh 15, m9. R. H. PASQS AL. M4965 FUSE I Filed July 3, 1944 RicharEdward Echramm F's-star T- ?atented 15, 1949 FUSE Richard H. Pass andEdward Schramm, Syracuse, and Foster T. Rhodes, De Witt, N. Y.,assignors to Onondaga Pottery Company, Syracuse, N. Y, a corporation ofNew York Application July 3, 1944, Serial No. 543,220,

9 Claims. 11

This invention relates to a chemical fuze for setting off or ignitingexplosives.

An object of the invention is the provision of a generally improved andmore satisfactory fuze in which the detonating action is initiated bythe chemical reaction of two or more substances upon each other.

Another object is the provision of a fuze of the pressure-operated type,so constructed that pressures of less magnitude than the predeterminedoperating pressure will not damage nor distort the fuze, and especiallywill not decrease the magnitude of pressure required to operate the fuzewhen it is again subjected to pressure.

Still another object is the provision of a fuze so designed andconstructed that no metal is contained therein, with the result that thepres.- ence of the fuze cannot be detected by magnetic or electricaldetecting means.

A further object is the provision of a simple and reliable fuze of achemical nature, adapted to a wide variety of uses, both military andcivilian.

A still further object is to provide a fuze which is perfectly safeagainst rough handling to any reasonable extent, and in which theoperating pressure required to set oil the fuze may be closelycontrolled within reasonable limits.

Other objects of the invention will be appar ent from the detaileddescription which follows, which description and the accompanyingdrawings are merely exemplary and are not intended to limit theinvention to the specific construction described.

In the drawings:

Fig. 1 is a central section taken longitudinally through a preferredembodiment of fuze in accordance with this invention, and

Fig. 2 is a transverse ection thereof taken substantially on the line 22of Fig.

The same reference numerals throughout the drawings indicate the sameparts.

Referring now to the drawings .and to the reference numerals markedthereon, a preferred embodiment of the invention comprises a tubularfuze body II of molded plastic material having intermediate its ends atransverse partition l3 provided with a central hole or aperture I5.Both ends of the tubular body II are internally threaded as shown.

Seated in the lower end of the body below the partition I3, is an ampulehousing 2| in the form of a plug of molded plastic material externallythreaded and screwed into the internal threads in the lower end of thebody I. This ampule housing has, near the upper end, a transverse bore23 extending approximately diametrically, and in this bore 23 is seateda tubular glass ampule 25 sealed at both ends and held in place at bothends by suitable cement 2?, such as plaster of Paris, preferably m xedwith a suitable indicator (such as Congo red, for example) sensitive tothe liquid within the ampule so that if any liquid leaks from the ampuledue to improper sealing, the plaster of Paris will change color and givea visual indication of the leak.

A longitudinal bore also extends centrally through the ampule housing2|. The supper portion 3| of this bore is of fairly large diameter,substantially larger than the diameter of the ampule bore 23, and formsthe primer cavity. The lower portion of the longitudinal bore is ofstepped formation, including a portion 33 of smaller diameter than theupper portion 3|, and another portion 35 of still smaller diameter. Apiston 37, also preferably of molded plastic material, is seated in andcapable of limited longitudinal movement in the portions 33 and 35 ofthe longitudinal bore, the piston being stepped so as to preventwithdrawal from the bore in a downward direction. The upper surface ofthe piston head is centrally depressed or recessed as shown at 38 sothat upon upward movement of the piston, contact with the glass ampule25 will occur only at approx mately the outer edges of the piston; Apiston retainer 39 in the form of a disc of somewhat flexible resilientmaterial such as a thin sheet of laminated phenolic material, is cutaway centrally and has inwardly extending spokes, one of which is shownat 4|, which enter an annular groove 63 in the lower portion of thepiston 37. The outer portion of the retainer 39 bears against the bottomof the ampule housing 2|, and the spokes 6|, being deflected somewhatupwardly to enter the groove 43, tend resiliently to hold the piston 3'7in its downward position, nevertheless permitting it to rise when upwardpressure is applied. The sides of the piston are preferably lubricatedwith low-viscosity grease to insure easy longitudinal movement of thepiston and to assist in excluding moisture from the primer cavity.

The glass ampule 25 has relatively thin walls easily broken bysubstantial pressure produced by upward movement of the piston 31.Sealed within this glass ampule is a quantity of activating agent 5| forthe primer mixture, this activating agent preferably being a solutioncapable of igniting the primer mixture upon more contact therewith whenthe glass ampule is broken. For the particular primer mixturehereinafter disclosed. excellent results are obtained by using, as theactivating agent, a solution of approximately 75% by volume ofconcentrated sulphuric acid, chemically pure, specific gravity 1.835 at20 0., and approximately 25% by volume of orthonitrotoluene. Preferablythe glass ampule 25 is only about 60% filled with this solution, so thata small air space is left. This facilitates the sealing of the ampuleafter the liquid is inserted.

The primer mixture is packed loosely all around the ampule 25 in theprimer cavity 3|, as shown at 53, and is retained in this primer cavityby a pressure disc 55 of thin plastic sheeting, cemented to the upperend of the ampule housing 2| around the edges of the cavity 3|, andfurther held in place by the partition I3 when the ampule housing 2| hasbeen screwed into and firmly seated within the body The bottom of theprimer cavity is formed mainly by the top surface of the piston 31. Theprimer mixture consists of one or more substances which will igniteimmediately on contact with the solution in the glass ampule. For usewith the particular activating solution hereinabove disclosed,

excellent results are obtained by using a primer mixture of potassiumchlorate and lead sulphocyanate, preferably in the proportions ofapproximately 55% by weight of potassium chlorate and 45% by weight oflead sulphocyanate. Both of these substances are finely ground in a ballmill so as to pass 325-mesh. and are thoroughly blended with each other.

0n the other side of the partition I3 from the primer mixture andactivating agent, there is a detonator comprising an inverted cup 6| ofplastic composition, the bottom end of which is closed by a suitableclosure 63 also of plastic composition. In this cup 5| there is an upperdetonator charge 65 and a lower detonwtor charge '51 of any suitabledetonating material. For example, the lower detonator charge may consistconveniently of lead azide compressed at a pressure of approximately4,000 pounds per square inch, and the upper detonator charge may consistof pentaerythrite tetranitrate (commonly known as PETN) likewisecompressed at a pressure of approximately 4,000 pounds per square inch.

Surrounding the detonator 5| is a booster pellet H of annular form. thedetonator being mounted in the central opening or cavity of the boosterpellet. This booster pellet may be of any convenient material, such as,for example, tetryl pressed to a specific gravity throughout of 1.40 to1.55.

overlying the partition I3, beneath the booster pellet II and thedetonator BI, is a booster disc 15 of thin material such as paraflinpaper. Overlying the booster pellet and the detonator is apad 15 ofsomewhat compressible resilient material, such as felt, held in place bya closure disc 11 preferably of molded plastic material, screwed intothe internal threads at the upper end of the body II with enoughpressure to compress the pad 15 slightly and thus hold the boosterpellet and the detonator firmly in place. Recesses 15 formed in theupper surface of the closure disc 11 may be engaged by means of aspanner wrench or special tool to screw the disc in place. The upper endof the body ll, above the closure disc I1, is preferably provided with acap 8| of any suitable design, preferably of molded plastic material,having for example a lower portion of reduced diameter. screwed into theinternal threads at the top of the body above the disc 11, and an upperportion of larger diameter provided with external threads 83 which maybe screwed into a suitable threaded opening in any article with whichthis fuze is to be used, such for example as an explosive mine, torpedo,shell, rocket, blasting equipment, or the like.

After the ampule housing 2|, with its contained activating solution 5|and primer mixture 53, has been screwed into place in the lower portionof the housing M, if the fuze is not to be used at once it may beprotected from accidental discharge by means of a safety cap 8| screwedinto the bottom end of the bod against an interposed gasket 93 of rubberor cork or both, to form a tight seal and prevent entrance of moisture.The safety cap has a central recess 95 providing ample clearance aroundth lower end of the piston 43, so that no pressure will be exerted onthe piston.

The fuze in its preferred embodiment above described is made entirely ofnon-metalli material so that it cannot be detected by magnetic orelectrical detecting means. If protection against such detection is notimportant, however, metal may be used for various structural parts suchas the main body II, the ampule housing 2|, the piston 31, the disc 11,and the caps 8| and 9|.

The operation of the fuze is as follows:

In order to prepare the fuze assembly for use, the safety cap 9| isunscrewed and discarded. The fuze assembly is then placed in appropriateoperating position with respect to any suitable form of actuatingmechanism, as for example by screwing the screw threads 83 into athreaded opening of a mine or torpedo in such position that, upon thehappening of a predetermined event or movement, upward pressure will beexerted on the piston 31. This upward pressure on the piston causesupward movement of the piston and, if the pressure is great enough,breaks the fragile glass ampule 25, allowing the liquid solution 5|therein to escape and come into contact with the primer mixture 53,which immediately ignites. The presence of the dis 55 at the top of theprimer cavity enables pressure in this cavity to build up when ignitiontakes place, and this pressure results in faster and more violentcombustion, which quickly consumes or breaks through the discs 55 and 13and passes through the flame hole I5 and causes immediate detonation ofthe detonating charges 55 and 51 in the detonator 6 and this causesimmediate and more violent explosion of the booster pellet II. Thisexplosion of the booster pellet shatters the entire body II andtransmits the explosion pressure to the main charge of explosive,surrounding or immediately adjacent to the body II or the fuze assembly,thus causing the main charge of explosive to explode.

Some of the advantages of the preferred construction, in addition tothose already mentioned, may be summarized as follows: The use of aglass container 25 of tubular form is found to give results muchsuperior to those obtained with a container of spherical form, forexample. An ampule made from glass tubing can readily be 7 made ofclosely controlled wall thickness, since glass tubing of controlled wallthickness is available. Consequently, since the wall thicknesses ofdifferent ampules can be kept substantially the same, the magnitude ofpressure required to break the ampule is reasonably constant for variousampules of the same design and dimensions. Constant breaking pressure(within reasonable limits) is, of course, a prerequisite to a fuze whichis intended to be set ofi by pressures of a given magnitude but is notto be set off by pressures of a lesser magnitude. As distinguished fromthe present very satisfactory construction a container of globular orspherical glass is unreliable and unsatisfactory because of the factthat there is not sufficient control over the wall thickness of glass inthis shape, with the result that different glass containers intended tobreak under the same magnitude of pressure actually are very erratic andrequire widely varying pressures to break them. Moreover, a globular orspherical container is dimcult to seal properly after the liquid isinserted therein. The tubular form of ampule is very easy to seal at theopen end after the liquid is-inserted therein, the liquid preferablyfilling only about 60% of the volume of the ampule.

The safety of the present construction is noteworthy. The glass ampule,after being seated in the ampule housing 2i and sealed therein by theplaster of Paris 2i, is protected on all sides by the housing 2i fromany accidental jar or blow which might fracture it during assembly ofthe fuze parts. In case there is a leak in the ampule due to impropersealing, the escape of acid will turn the Congo red in the plaster ofParis 2? to a blue color, so that when the ampule housing 2! is pickedup by the person assembling the fuze parts, to be screwed into the mainbody ii, any change in color of the plaster of Paris can immediately beseen and thus a leaky ampule can be detected. Moreover, with thisconstruction, there is no substantial danger of premature firing even ifthere is a leak in the ampule, because the plaster of Paris itself formsa seal preventing any liquid which may leak out of the sealed endof theampule from coming into contact with the primer mixture 53.

Another important feature of this construction is that subjecting thefuze to any pressure less than that required to break the ampule doesnot lower the magnitude of the pressure required later to break theampule and set off the fuze. When a pressure-sensitive fuze is providedwith a shear pin to determine the extent of pressure required to set offthe fuze, as has been proposed in the past, it may happen that apressure almost, but

'not quite, great enough to shear the pin completely, may causedeformation and partial shearing of the pin, without setting 01f theiuze. Then, when pressure is again applied to the fuze at a later time,it may require only a very slight pressure, much less than the intendedcritical magnitude, to complete the shearing of the pin and to set oilthe fuze. The serious dangers in any such construction are apparent.With the present construction, however, if the pressure is notsufiicient to break the glass ampule, it does not affect the ampule atall, and when the'uuze is again subjected to pressure at a later time,it still requires the full predetermined magnitude of pressure to breakthe ampule and set off the fuze;

The recessed shape of the head of the piston 31 results in applying tothe glass ampule a shear load just inside the ampule holding ring,formed by the upper part ofthe housing 2!. This results in quickerbreaking and quicker escape of the contents of the ampule, when broken,and thus in quicker igniting action, than would be the case if thepiston pressure were applied near the center of the unsupported portionof the ampule.

Another factor which aids in securing the dein the ampule. The additionof the orthonitrotoluene lowers the freezing point of the sulphuricacid, enabling the mixture to run rapidly out of the broken ampule attemperatures even as low as minus 40 F., whereas sulphuric acid alonewill freeze at considerably higher temperatures, which would make thefuze inoperative. The orthonitrotoluene also acts somewhat as acatalyst, greatly speeding up the ignition action of the acid. Althoughother acids may be used as igniting agents, sulphuric acid givesconsistently faster ignition than other common acids, such as hydrochloric acid and nitric acid, and is the only one of these acids whichis miscible with orthonitrotoluene. The combination of sulphuric acidand orthonitrotoluene remains fast in action and stable at alltemperatures from minus 40 F. to plus 170 F., and thus provides anactivating agent which is very satisfactory over a wide range oftemperatures.

Another feature to be noted is the composition of the primer mixture,preferably potassium chlorate and lead sulphocyanate, as above stated.Broadly, it is possible to use a mixture of (a) any substance which willignite spontaneously upon contact with the activating agent, and (b) anyoxidizing compound, to furnish the necessary oxy gen to support rapidcombustion. Good results can be obtained by using, as the ignitablesubstance, lactose or sucrose or hexamethylenetetramine or guncotton orbenzoic acid or pentaerythrite, for example, and by using, as theoxidizing compound, MnOz or NaClOa or NH4C1O4, for example. However,some of these substances are highly hygroscopic, which undesirablydelays the fuze action when used in a humid atmosphere.

The best results, from the overall standpoint of rapid action throughoutthe desired wide temperature range and stability against deteriorationat extreme temperatures, have been obtained by using the preferredmixture above disclosed, namely, lead sulphocyanate as the ignitablesubstance and potassium chlorate as the oxidizing compound. This mixtureis substantially non-hygroscopic. Small amounts of other substances maybe added to the mixture (e. g. charcoal or guncotton or benzoic acid orred phosphorous) but no consistent improvement is thereby obtainedexcept in the case of red phosphorous, and this material is far toofriction-sensitive to be safely used.

Still another feature aiding in the quick action of the fuze is theabove-described fine grinding of the ingredients of the primer mixture53. When these ingredients are ground to a fineness of the order ofmagnitude above described. it is from coarser mixtures, but thepreferred grinding 50 as to pass a 325-mesh gives even better results.

Each of the factors above mentioned in connection with the speed of thefuze may in itself give only a slight increase in speed, amounting toonly a small fraction of a second, but when all of these factors areused conjointly in the preferred form, there is a substantial andnoteworthy increase in speed, the fuze ordinarily operating to causeignition of the detonator charges and 67 within about one-tenth of asecond or less after the necessary pressure is applied to break theampule. The importance of having a fuze capable -of such fast action isseen when it is realized that a vehicle traveling at, say, fifty milesan hour is only over a given point on the road for a small fraction of asecond. If it is intended to have the weight of the vehicle actuate thefuze and blow up a mine planted in the road, a delay of one second oreven half of a second in operation of a fuze may result in the mineexplosion taking place after the vehicle has safely passed over themine. The effectiveness of the mine is greatly increased by using anextremely quick-acting fuze constructed in accordance with the preferredembodiment of the present invention.

While one embodiment of the invention has been disclosed, it should beunderstood that the invention may be carried out in a number of ways.This invention is not to be limited to the precise details disclosed,but is intended to include all variations and modifications thereoffalling within the scope of the appended claims.

What is claimed is:

1. In a fuze for explosives, the combination of a member having thereintwo openings intersecting each other, one of said openings being oflarger diameter than the other in the region of intersection, afrangible liquid-tight container of generally elongated tubular shapehaving its intermediate portion extending across said region ofintersection and its ends mounted in one of said openings, a liquidactivating agent including acid in said container, said region ofintersection of. said openings being adapted to hold a combustibleprimer substance sensitive to said acid to be ignited thereby when saidcontaineris broken, and cement holding the ends of said container insaid openings, said cement including an acidsensitive color-changingsubstance to provide a visual indication of leakage of acid from an endof said container.

2. A fuze for explosives comprising a frangible liquid-tight receptaclecontaining sulphuric acid and orthonitrotoluene, and a primer mixtureadjacent said receptacle in position to come into contact with thecontents of said receptacle when the receptacle is broken, said primermixture including a combustible substance capable of being ignited bycontact with the contents of said receptacle, and an oxidizing agent.

3. A fuze for explosives comprising a frangible liquid-tight glassreceptacle of generally tubular shape containing a mixture of sulphuricacid and orthonitrotoluene in the proportions of approximately 75%sulphuric acid and approximately 25% of orthonitrotoluene, and a primermixture adjacent said receptacle in position to come into contact withthe contents of said receptacle when the receptacle is broken, saidprimer mixture including lead sulphocyanate and potassium chlorate.

4. A fuze for explosive comprising a frangible liquid-tight receptaclecontaining sulphuric acid and orthonitrotoluene, and a primer mixtureadjacent said receptacle in position to come into contact with thecontents of said receptacle when the receptacle is broken, said primermixture including lead sulphocyanate and potassium chlorate both in theform of finely ground powders intimately blended with each other.

5. The combination claimed in claim 4, in which said powders are of afineness capable of passing a 325-mesh screen.

6. A non-metallic fuze comprising in combination a cylindrical body, afrangible liquid-tight container containing a liquid activating agentmounted within the body, the axes of said body and said container beingat substantially right angles with each other, a piston disposed withinsaid body adapted to slide axially relative to said body and to contactsaid frangible container, a primer substance adjacent to said frangiblecontainer, an annular recess on said piston and a perforated disc ofresilient material, the inner portion of said disc fitting into therecess and the outer portion of said disc being retained by the body,said disc tending to keep the piston from contacting the frangiblecontainer.

7. The fuze of claim 6 in which the disc comprises a thin sheet oflaminated phenolic material. 8. The fuze of claim 6- in which the discis perforated so that inwardly directed spokes are formed, the innerends of said spokes fitting into the annular recess on the .piston.

9. A fuze for explosives comprising a frangible liquid-tight containerof generally tubular form. means for supporting said container at twospaced points, a liquid activating agent within said container, acombustible primer substance sensitive to said activating agent closelyadjacent said container, and a member mounted for movement toward saidcontainer in the space between said points of support, to break saidcontainer to release said activating agent for contact with said primersubstance to ignite the same, said activating agent including sulphuricacid and orthonitrotoluene, and said primer substance including leadsulphocyanate and potassium chlorate.

RICHARD H. Pass. EDWARD SCI-IRAMM. FOSTER 'r. RHODES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 42,185} Ganster Apr. 5, 18642,133,119 Smith Oct. 11; 1938 2,328,276 Hunt Aug. 31, 1943 FOREIGNPATENTS Number Country Date 18,659 Great Britain Apr. 14, 1912 62,857Switzerland Apr. 17, 1913

